1. Field of the Invention
The present invention relates to a MUSE (Multiple Sub-Nyquist Sampling Encoding) signal digital recording/reproducing apparatus for recording/reproducing MUSE signals in digital VTRs and an operation method thereof, and particularly to an adaptor for converting a MUSE signal in correspondence to recording/reproducing formats of a high definition television signal recording/reproducing device (hereinafter, referred to as a HDVTR) capable of digitally recording a high definition television signal.
2. Description of the Background Art
The MUSE system has been recently developed and the test broadcasting of high definition television signals has been started with the development of the MUSE system.
The MUSE system is a system in which a high definition television signal is compressed to a signal with baseband width of approximately 8 MHz. A signal converted according to the system is referred to as a MUSE signal.
For recording/reproducing a MUSE signal, two kinds of methods are presently proposed. One of them is a method for recording/reproducing a MUSE signal as it is by a VTR dedicated to a MUSE signal, and another one is a method in which the rate of a MUSE signal is converted into the input format of a digital VTR of the standard system to be recorded, and when reproducing, conversion opposite to that in recording is performed to produce a MUSE signal. The former method can record a MUSE signal as it is, so that the recorded signal can be extracted to evaluate the quality of the inputted MUSE signal. For manufacturing a VTR dedicated to MUSE signal, however, great amounts of time for development and cost are required. Accordingly, with the latter method less time for development and less cost are required as compared to the former one. The latter method is disclosed in "ITEJ Technical Report Vol13. No.50 p.p.25-30, VTR' 89-16C Oct. 1989".
FIG. 10 is a simplified block diagram of the recording system described in the paper. The recording system includes a digital VTR (hereinafter, referred to as a VTR 50) of the SMPTE-D-1 standard, and an adaptor 51 for converting a MUSE signal so that it conforms to the input rate of VTR 50. A MUSE signal dealt with herein is converted digital data of 16.2 MHz, 10 bits.
Adaptor 51 includes an interface portion 52, a rate converting portion 53 and a system controller 54. Interface portion 52 performs re-arrangement of data corresponding to the standard of VTR 50 and also adds a control code for controlling VTR 50. Rate converter 53 converts the rate between an input source of MUSE signal and interface portion 52. System controller 54 produces a signal for recording an inputted MUSE signal in VTR 50 in synchronization with VTR 50 and all control signals used inside adaptor 51.
FIG. 11 is a diagram for describing a rate converting operation of adaptor 51. Referring to the figure, M denotes a higher bit and L denotes a lower bit. Firstly, a MUSE signal of 16.2 MHz, 10 bits is applied to rate converter 53 and converted into digital data having the input rate of interface portion 52 (13.5 MHz 8 bits.times.1, 6.75 MHz 8 bits.times.2). The three time-divided digital data are converted into 27 MHz 8 bits (the input rate of VTR 50) by interface portion 52 and then provided to VTR 52.
As described above, since a MUSE signal of 16.2 MHz.times.10 bits can be converted into digital data of 27 MHz.times.8 bits which is the input rate of VTR 50, even when the bit lengths of a recorded signal of VTR and a MUSE signal are different, the MUSE signal can be recorded in recording tape.
While frame frequency of a MUSE signal is 30 MHz, frame frequency in the NTSC system is 29.97 MHz. Since frame frequencies of the two are thus different, respective frames of MUSE signal recorded in VTR 50 are simply handled as continuing signals as shown in FIG. 12. Also, regarding information amount, while it is 20M bite/second in a MUSE signal, it is 21.57M bite/second in a recorded signal of VTR 50. Accordingly, the capacity of VTR 50 is larger and data can be recorded without loss. Furthermore, it is described in the above-identified paper that a signal of double rate (32.4 MHz.times.10 bits) can be recorded/reproduced by adding VTR 50 and a frame memory board.
The adaptor is enough to simply record/reproduce a MUSE signal and to be used as a MUSE source. However, as described above, since frame frequencies of a MUSE signal and a recorded signal of VTR differ from each other, frame lock is impossible. Therefore, coupling VTR 50 to a simulator for video signals, in processing recorded data in frame units, or in evaluating quality of a MUSE signal on the basis of recorded data, or in evaluating a system of data compression, a problem occurs.
The inventors of the present invention focused their attention on usage of a so-called HDVTR capable of recording with the same frame frequency as a MUSE signal and having a large recording/reproducing capacity. The HDVTR, however, uses only effective lines and effective picture elements of a high definition television signal as record information, so that it has a problem that a MUSE signal having different numbers of picture elements and lines from those of baseband can not be directly recorded.